VE311 Electronic Circuit HW3
Due: Jun 11th 11:59 a.m.
Note
1. Please use A4 size paper or page.
2. Please clearly state your final result for each question.
3. Please state and verify the operating region (cutoff, FAR/active, or saturation) of each BJT.
Problem 1
An npn transistor of a type whose β is specified to range from 50 to 300 is connected in a circuit with emitter grounded, collector at +10 V, and a current of 10 µA injected into the base. Calculate the range of collector and emitter currents that can result. What is the maximum power dissipated in the transistor?
(Note: Perhaps you can see why this is a bad way to establish the operating current in the collector of a BJT.)
Problem 2
A very simple circuit for measuring β of an npn transistor is shown in Fig 1. In a particular design, VCC is provided by a 9-V battery; M is a current meter with a 50-µA full scale and relatively low resistance that you can neglect for our purposes here. Assuming that the transistor has VBE =0.7 V at IE =1mA, what value of RC would establish a resistor current of 1 mA? Now, to what value of β does a meter reading of full scale correspond? What is β if the meter reading is 1/5 of full scale? 1/10 of full scale?
Problem 3
For the circuit in Fig 2, find VB and VE for vI = 0V, +2V,–2.5V, and –5V. The BJTs have β=50.
Problem 4
For the circuit shown in Fig. 3, find the labeled node voltages for:
(a) β = ∞;
(b) β = 100;